Fuse plug



Sgpt. 21, 1926.

H. L. STRONGSON FUSE PLUG Filed Nov. 6, 1922 IN VEN TOR nypo i ATTORNE YPatented Sept. 21, 1926.

l UNITED STATES unman L. s'rnonosou, or BROOKLYN, NEW Yo n's s xonon"rofsritonoson Urn ITIES CORPORATION, or NEW YORK, N. Y., a conrom 'rronorjnnw you,"

rusn PLUG.

Application filed November 6, 1922. sena1'no.-599,21s.

I v This invention relates to fuse plugs and more particularly toimprovements in renewableindicating fuse plugs, and consists inimprovements over my patent application Serial Number 582,121 filedAugust 16,

Primarily the object of the present invention is to provide asimple fuseinexpensive to manufacture, which is positive in its indicatingfunction, and which indicates a blown or burned fuse upon the rupture ofthe said fuse link caused either by short-circuiting or an over-loadcurrent; and an additional object is to improve indicating fuse plugs byernploying a combined pressure indicator actuated by the heat andpressure liberated by the burned or exploded fuse link together with ameans for spring pressing the-said indicator outwardly to visibleposition.

Though I have, as a mattercof course. certain objects and ends in viewwhich are mainly similar to those of other inventors as expressed in theprior art, I provide a dif ferent structure and it is with my actuallyimproved fuse plug structure embodying a rearrangement andre-organization of parts which enables me'to produce a reloadableindicating fuse plug which, in practice ac complishes and carriesout thepurposes and 30 exoelsin function the performance of known fuse: plugs,and commercially functions to meet all requirements which are not met byother patented devices. 4 I

' v The accompanyingdrawings illustrate'an exemplary embodiment of myfuse plug serving to explain the principle ofthe invention which may beadapted to various modifiedstructures to better suit the needs ofmanufacturers'and users.

Figures 1, 2 and 3 illustrate, respectively,

top, side; and bottom projections of the fuse plug a a 4 ternalstructure thereof.

moved from the reload indicating plunger placedin position and madeready tobe pressed down on the terminals prior to inserting the reloaiedparts in the cover barrel or fuse'plug body. at

later described, and is provided with a cen- "Fig-ure 4 illustrates anenlarged ilongitudia nal section of the fuse plug showingthe in- Figuredis a perspective view ofthe in} dicatingr'eload fuse plug with the coverre and closure cap together with a fuseribbon' 1 Figure 6. shows anenlarged v'iew of the reload cap and plungerremoved from'the'fuse plugbody or cover with a new 'fuse. ribbon in position' I,

Referrin now more particularly to the drawings or a detailed explanationof an embodiment of my invention, there is shown a reload plug cap orbarrel closure plug comprising a knurled grip 9 with stepped or reducedbosses or portions 10 and 11 which function as sealing shoulders to makea flame tight structure though permitting the clo-- sure cap 9 to beeasily removed from the fuse plug body. This reload or closure cap ismade with an internal bore or molded core 12 for the reception of theindicator as ter contact 13,'and a fuse terminal 14:; The fuse terminal14 joins the contact screw 13, or the screw may be omitted inasmuch asthe terminal 14 is exposed at the end of the fuse plug. The upper'endof'the fuse terminal 14 is preferably flexible or spring lil re and isadapted to flex inwardlya'g'ainst'the boss portion 1'0-when the fuseplug cover'is applied; and this" part 14 is preferably eI'Iibedded ormolded in the cap, as"sho:wn,'to produce a substantial rigidconstru'ctionl' The plug cap 9'11 'i's alsoprov'ided with anotherterminal preferably punched from sheet material consistingof a plate 15an-" chored to the cap, and the plate has a close 1y spaced fuseterminal 16 and'out side con- I tact 17. The two parts 16 and17"preferablyii possess springiness or, yieldability so: make effectiveelectrical contactwith parts engaging them'gand the contacts 16 and'17 fare integral withtlie plate '15 'as*observed.; This member 15 is moldedor straw-fastened tothe part 10; andthetwo'fus'e terminals 14" and 16are preferably oppositely {disposed forthe convenient reception of thefus'eribbon ends as will "be-"described; An indicating 'plungerhasamine-mating head 19'withanintegrah res'surpisto' 20} and a sleeve"21. I The indicator-s1 sl'i'dably' confinedin the bore 12bit by anysuitable-'mjeans'such "asby pin; 22" anchoredin the upper part of the'ca'p 9 with V its' end projecting'intoa groove E23 in""the sleeve 21which holds th'e parts together ear-1; ing the. reloading operationwhile th'' capt" and indicator 19areoutofthefuseplug body cover to bedescribed. A light coil spring 24 is confined in the plunger sleeve .21with its lower end bearing against the bottom of the bore 12 therebytending to force the indicator 19 upwardly. The indicator 19 is providedwith a fuse receiving hole 25 below the piston through which a fuseribbon is inserted as shown in Figure 5.

A threaded cover barrel or fuse plug body 28 is provided with a knurledhand grip 29 by which it is screwed into the receptacle. The upper endof the plug body 28 is provided with a hole or indicating orificethrough which the indicator 19 projects when the fuse is blown orruptured, and the lower end of the fuse plug body or cover barrel isopen to receive the reloaded indicator and cap; and this body comprisesa cylinder in which the piston 20 moves upwardly to expose theindicator. ternal threaded surface of the fuse plug body 28 is providedwith a longitudinal groove 30 into which slides the outside contact 17when the parts are assembled. lnternal grooves 31 and 32 are made in theplug body 28 for the sealed reception of the fuse terminals 1e and 16,the said larger groove 31 fitting over and sealing the fuse terminals 15and 16, and the opposite groove 32 fitting over and sealing the otherterminal 14.

The fuse plug is reloaded with, as for example, a standard type fuselink such as shown in the drawings, which usually possesses enlargedcontact ends 34; and a centrally reduced fusing thread portion 35; andthe fuse ribbon is inserted through the hole 25 while the plunger 19 andcap 9 are pressed together; and thereafter the two fuse ends 34 arefolded down over the fuse terminals 14 and 16 such as is shown inFigures 4 and 6. The hole 25 in the indicator plunger acts as acentering means by which, in loadin the plug fuse, one may quicklyperceive a bout when the center art of the fuse thread 35 is in positionor folding down the ends 34. By gripping the fuse ends 34 onto theterminals between the thumb and finger, the indicating plunger is helddownwardly as the fuse plug cover 28 is placed in position over thereloaded element, and the fuse is then ready for'use.

After the plug is assembled it is screwed into a fuse plug receptaclesocket, the outside contact blade 17 yielding inwardly in contact withthe metal shell of the receptacle thereby establishing positive contact;and the center contact 13 seats against the center receptacle contactinto which the fuse plug is screw-inserted. The electric circuit is thencompleted through the plug by running from the side contact 17 throughthe fuse terminal 16, through the fuse and thence downwardly through thefuse terminal 14 to the center contact The ex-' When the fuse thread 35burns or explodes due to a short-circuit in the line, the gases and heatliberated produce a powerful upward thrust under the piston 20 reactingagainst the upper face of the closure cap portion 11, and quicklyprojects the indicator 19 into exposed position. In a similar mannerwhen the fuse ruptures under an overload current value, the pressuregenerated by the heat liberated is largely accentuated by the spring 24causing the plunger to quickly rise through the head 29 of the fuse plugbody producing a positive indication. The piston 20, when it shootsupwardly against the upper end of the cylinder, effects a sealed jointagainst the inner surface of the cover where the indicator head projectsthrough thereby stifling the arc and flame and preventing a discharge offire from the plug.

The indicator piston 20 seals the upper end of the fuseplug and the cap911 seals the lower end thereof against escape of fire when the fusemelts, yet the piston and indicator head afford a ventin means in thenature of a tortuous passage by causing the fuse gas to escape aroundthe circumference of the piston and inwardly toward the indicator andfinally out of the plug body through the slight clearance afforded forthe free movement of the indicator head 19.

It is to be noted that the piston 20 occu pies a position relativelycentral with respect to the parts 19 and 21 which extend therefrom; andin this arrangement there are accomplished several important func' tionswith a single piece of structure. For exam 1e, the piston, so to speak,divides off the plug fuse into a lower portion containing the workingparts and an upper portion affording space and volume for dissipatingthe heat and gases, for it is to be appreciated that, as the piston 20moves upwardly in the cylinder, the volume or space under the piston inwhich the fuse burns is increased which allows a natural expansion ofthe fuse gas thereby more easily spending the force and energy'of theheat liberated by the burning fuse; and while this is not itself broadlnew, it is novel in a simple renewable indieating fuse plug capable ofquick reloading operation, for I have adapted this useful principle tomy new improvements and reorganization of structural arrangements overthe prior art. The lower stem 21 projects from the piston and isslidably confined the removable closure cap thereby holding together theplunger and cap as a unit 9-19 when the body 28 is removed for reloadpurposes which afi'ords convenicLce and eliminates the replacing ofloose parts back into the threaded body 28, for it is to be appreciated,as in Figure 5. the devi e only separ a tes lCIIIiZO two parts whenreloading is to be cnecte needed to holdthe cap 9 in the cover bodybecause the receptacle into which the plug fuse is screw inserted holdsthe cap in: place against the most forceful burning of a fuse;

and in the same manner no metal shell is necessary for contact purposes,for the flat broad blade 17 adequately provides for this requirement.Furthermore my contact and terminal arrangements, whereby the contact 17and terminals 14 and 16 register in grooves of the cover, rigidly holdsthe cover and reload unit in fixed relation to prevent the cover 28 fromturning on the cap 9. In other devices it has been necessary to employscrew shells for this purpose which handicaps reload operations.

The construction of my plug fuse accommodates a fuse ribbon ofsubstantial length and enables the fusible portion to be positioned wellup into the body of the device thus segre ating the metal fuse terminalsfrom the f using part of the fuse element. Furthermore, I do not in anyway permit the spring 24, which assists the indicator in projectingitself into view, to come in contact withthe, renewable fuse ribbon. forinsulating material completely encloses the spring v t I v The flat ends34 of a conventional fuse link, which myplug fuse receives, very readily lap down against the terminals, for it is to be appreciated thatthese fuse ends dc not have to be hooked over or folded under terminalparts. While it may be suggested that renewable flat fuse ends'may beheld in place by a metal screw shell or by a metal ring, being extraparts, I cause the plug body itself to perform this function. I explainthis feature of my structure because of the extreme difliculty oneencounters in trying to fasten a soft delicate fuse link over hooks,prongs or even under a brass screw shell as it shown in\ some patents.

Spring pressed plungers and indicators are known in the. art and largelysuggested as a means for quickly separating the burning fuse ends toquickly extinguish the arc;

and in some instances a plunger may be employed to jump between theburning fuse ends to, act as a barrier. In my invention I have otherobjects in View in the use of my spring 24 for indeed my plug fuse neednot have its terminals-separated,,nor its fuse ends jerked apart, forsuch action sometimes causes a premature rupture oflthe. link and theunnecessary interruptionof the supplyof current. The terminals ofthisfuseplug are sealedin between two pieces of insulation and are never.damaged by the 'arcing of the, fuse. There is not one single piece ofmetal,

nor fixtures, nora spring part,or-other sub stance, within the fuseburning chamber ex cept the fuse link, andconsequently no dan ger existsas to the'drawing'out or -prolonga-' '70 tion of the fuse burningperiod.

This fuse plug is easy to reload, possesses few parts, and enables oneto quickly locate a blown fuse plug among many others, even in darkplaces.

What I claim is 1. A fuse plug comprising, an externally threaded fuseplug body provided with one end open and an indicatin orifice in theother end, a closure cap i emovably closing the open end of the body, anindicator mounted on the closure cap and projecting into the indicatingorifice and adapted to move relatively to said cap parallel to the axisof the fuse plug body and cap, means positively holding the indicator onthe cap so that the cap and indicator are removed and replaced as a unitfrom the body, fuse terminals to engage a renewable fuse link, and plugcontacts connecting with the fuse terminals.

2. In fuse plug improvements, a fuse plug body externally screw-threadedand open at one end, a removable closure cap provided with alongitudinal bore and adapted to seal the open end of the plug body, anindicator projectable from the fuse plug body and slidably confined inthe bore of the cap, a. spring to exert an'outward thrust on theindicator, fuse terminal and plug contacts, and fuse link receptionmeans to carry aflfuse in a way to engage and hold inwardly theindicator.

ing an open-ended fuse plug b0 y, a removable closure cap to seal up thebody, an in-, dicatorrnovably carried on the cap and removable from thebody with the cap, a spring 3. Improvements in fuse plu s, compris-Yinterposed between the indicator and cap to exert force against theindicator, fuse terminals, a fuse link reception means to carry a fuseengaging the indicator to hold 1t down on the closure cap, and fuse plugcontacts connecting with the terminals.

4. Improvements infuse plugs comprisng a threaded plug body knurled onone end for a hand-grip and open at the other end, a.

removable cap adapted to close the plug and provided with a centralbore,'an indicatonslidably confined in the cap bore, a spring in the capbore exerting an indicating force against the indicator, means onthe'indicator for receiving a reload fuse link, fuse terminals adaptedto engage the fuse link ends and hold the indicator down when assembled,and fuse plug contacts connecting with the fuse terminals.

5. Improvements in fuse plugs comprising a threaded body with one endopen and the other end having a restricted indicating opening, aremovable closure cap to seal the bodv and close it at one end, anindicator confined in the restricted body opening to close the other endof the body, a plunger made on the indicator and extending into the capand slidably carried thereby and removable with the cap from thethreaded body for reloading purposes, fuse link holding means relatedwith the plunger and the cap which receives a fuse link that holds theindicator in compressed relation upon the cap, fuse terminals to engagethe link, and plug contacts connecting with the fuse terminals,

6. Improvements in fuse plugs comprising a plug body having an endthereof made open, a removable closure cap to seal the open end of thebody, an indicator projectable from the plug body, means for securingthe indicator and cap together in a movable relation to prevent theirseparation when removed from the body for reload purposes, fuseterminals to engage the link, and fuse plug contacts connecting with thefuse terminals.

7 Improvements in fuse plugs comprising a body open at one end, aremovable cap to seal the open end of the body, an indicator movablycarried on the removable cap, a spring interposed between the cap andindicator to exert an indicating force, fuse-terminals carried on theremovable cap which engage a fuse link to hold down the indicator, andfuse plug contacts which connect with the fuse terminals.

8. Improvements in fuse plugs comprising a body open at one end, aremovable cap to seal the open end of the body, an indicator movablycarried on the removable cap, a spring interposed between the cap andindicator to exert an indicating force, fuse terminals carried on theremovable cap which engage a fuse link to hold down the indicator, acenter fuse plug contact on the cap connecting with one of the aforesaidfuse terminals, and a side fuse plug contact integral with the otheraforesaid fuse termi nal and extending outwardly from the sealed bodyand cap.

9. Improvements in fuse plugs comprising a plug body open at each endand externally screw threaded, an indicator slidably retained in oneopen end to close that end of the body, a removably reloadable closurecap adapted to seal the outer end and provided with a longitudinal bore,a sleeve extending from the indicator into the bore of the cap of toremove it from the opening in the body, an indicating plunger movablycarried by the cap, a spring to urge the indicator away from the cap,fuse link receiving means to hold the indicator down when reloaded, fuseterminals forming part of the means, and fuse plugs contacts connectingwith the terminals.

' 11. Improvements in fuse plugs comprismg a plug body with anindicating opening and internal cylinder bore and external screw threadsand being open at one end and having a knurled hand portion, a closurecap knurled for the convenient gripping thereof to remove it from theopening in the body, an indicating plunger movably carried by the cap, aspring to urge the indicator away from the cap, fuse link receivingmeans to hold the indicator down when reloaded, fuse terminals formingpart of the means, fuse plug contacts connecting with the terminals, anda piston carried by the indicator reciprocable in the aforesaid cylinderto accentuate the spring urged indicator and to seal the indicatingopening.

12, Improvements in fuse plugs comprismg a fuse plug body made with aninternal cylindrical bore and being open at one end, a. removablereloadable closure cap fitted into the open end of the body, a pistonslidably confined in the bore, an indicator carried by the piston andprojectable from the plug body, a part integral with the piston andprojecting down into the reloadable closure cap, means for movablysecuring the said part onto the cap to prevent separation thereof,reload fuse terminals and fuse plug contacts carried on the cap.

13. In fuse plug improvements, a hollow plug body with one end open andan indicating orifice in the other end, a removable reload closure capfitted in the open end of the body, an indicating plunger carried on theinner end of the closure cap being slidably related therewith and fixedagainst detachment from said cap, a resilient means for urging theplunger to an indicating position,

fuse terminals and plug contacts carried on the cap.

14. In plug fuse improvements, a hollow body for insertion into areceptacle base and to contain plug fuse parts, said body being open onone end and having an indicating orifice at the other end, a removablereloar closure cap designed to close the open end of the body, anindicating plunger movable in the body with one end thereof slidablyrctained against detachment withinthe closure cap and the other plungerend shdably con- 1 fined in the indicating orifice, fuse terminals andplug contacts carried on the cap.

15. In plug fuse improvements, a hollow body for insertion into areceptacle base and to contain plug fuse parts, said body be ng open onone end and having an indicating orifice at the other end, a removablereload closure cap designed to close the open end of the body, anindicating plunger movable in the bodywith one end thereof s'lidably'retained against detachment within the closure cap and the other plungerend slid' of the body, an indicating plunger movable in the body withone end thereof slidably retained against detachment within the closurecap and. the other plunger end slidably ably confined in theindicatingorifice, a'piston carried in the hollow body and designed to produce anupward thrust upon the indicator when a fuse burns, and fuse terminalsand plug contacts carried on the cap.

17. In lug fuse improvements, a hollow body for msertion into areceptacle base and to contain plug fuse. parts, said bod being open onone end and having an in icatin orifice at the other end, a removablereloa closure ca designed to close the open end of the bot? anindicating plunger movable in the bo y with one end thereof slidablyretained against detachment within the closure cap and the other plungerend slidably confined in the indicating orifice, a piston carried by theindicator, said indicator provided with a fuse receiving holeadj acentthe piston, and fuse terminals and plug contacts carried on the cap. a

18. In plug fuse improvements, a hollow body for lnsertion into areceptacle base and to contain plug fuse parts, said bod being open onone end and having an in icating orifice at the other end, a removablereload closure cap designed to close the open end of the bod anindicating plunger movable in the ho y with one end thereof slidablyretained against detachment within the closure cap and the other plungerend slidably confined in the indicating orifice, a piston carried in thehollow body and designed to produce an upward thrust upon the indicatorwhen a fuse burns, and fuse terminals and plug contacts carried on saidcap, and a spring to accentuate the upward thrust of the piston to urgethe plunger to indicating position.

19. A plug fuse comprising a body made of insulation with one end openand threaded to screw into a fuse receptacle base, a knurled hand gripon one end of the body, a closure cap designed to seal the open body endand removable for inserting a renew fuse, an indicating plunger slidablycarried upon carri thej c p and fixedagainst eas ment "was,

lug contacts 7 the; ca", fuse terminals and I on' the cap, and a'knur edgrip made on the cap .by which'the plug fuse may be,

gripped'by the two aforesaid knurledparts and opened, forf'reloadingoperation. I 20. Aplug fuse comprising a body made of insulation withone, end open and threaded to screw into a fuse receptacle base, a

knurled hand grip on one end of the body, a. closure cap designed toseal the open body end and removable for inserting a renew fuse, anindicating plunger slidably carried upon the cap and fixed againstdetach- 'ment with the cap, a spring urging outwardly on the indicator,fuse terminals and plug contacts carried on the cap, and a knurled gripmade on thecap by which the plug fuse is gripped for separation thereof.

21. A plu fuse comprising an externally threaded ody open at one end andhaving a cylindrical bore, a removable reloadab e cap fitting into theopen end of the body, said cap made with a bore, an indicator plungerextending through the cylindrical ore of the body, a tubular stem madeon the lower end of the plunger and slidably mounted in thebore of thecap, a spring confined in the cap bore and tubular stem to urgeoutwardly on the indicator, fuseterminals and lug contacts carried onthe ca 22. AP u fuse comprising an externally threaded y open at one endand having a cylindrical bore, a removable reloadable cap fitting intothe open end of the body, said cap made.with, a bore, an indicatorlunger extending through the cylindrical ore of the body, a tubular stemmade on the lower end of the plunger and slidably mounted in the bore ofthe cap, a sprin confined in the cap more to urge outwar y on theindicator, a iston carried b the plunger and reciproca le in the cylinder bore, and fuse terminals and plug contacts carried on the cap.

23. A plu fuse comprising an externally threaded b y open at one end'andhaving a cylindrical bore, a removable reloadable cap fitting into theopen end of the body, said cap made with a bore," an indicator plungerextending through the cylindrical bore of the body, a tubular stem madeon the lower end of the plunger and slidably mounted in the bore of thecap,'a spring confined in the cap bore to urge outwardly on theindicator, a piston carried b the lunger and reciprocable in the cyinder ore, andfuse terminals and plug contacts carried on the cap.

24. A plug fuse comprising a threaded bod with inside cylindrical bore,said'body ma e open on one end and a groove formed through the threadsof said body, a ca to seal the open plug end, a side contact b ade theaforesaid groove, a fuse terminal integral with the contact blade andsealed between the body and cap, another fuse terminal locatedsubstantially opposite to the first named fuse terminal and similarlysealed, a center contact on the cap making connection with the lastnamed fuse terminal, an indicating plunger slidably carried by the cap,and means related with the plunger to receive a renew fuse link engagingand holding down on the indicator.

25. A plug fuse comprising a threaded body with inside cylindrical bore,said body made open on one end and a groove formed through the threadsof said body, a cap to seal the open plug end, a side contact bladecarried by the cap and adapted to slide into the aforesaid groove, afuse terminal inte gral with the contact blade and sealed between thebody and cap, another fuse terminal located substantially opposite tothe first named fuse terminal and similarly sealed, a center contact onthe cap making connection with the last named fuse terminal, anindicating plunger slidably carried by the cap,

means related with the plunger to receive a renew fuse link engaging andholding down on the indicator, and a spring urging outwardly on theindicator.

26. A plug fuse comprising a threaded body with inside cylindrical bore,said body made open on one end and a groove formed through the threadsof said body, a cap to seal the open plug end, a side contact bladecarried by the cap and adapted to slide into the aforesaid groove, afuse terminal integral with the contact blade and sealed between thebody and cap, another fuse terminal located substantially opposite tothe first named fuse terminal and similarly sealed, a center contact onthe cap making connection with the last named fuse terminal, anindicating plunger slidably carried by the cap, means related with theplunger to receive a renew fuse link engaging and holding down on theindicator, a spring urging outwardly on the indicator, and a pistoncarried by the indicator.

In testimony whereof I affix my signature this 4th day of Nov., 1922; inthe county of New York, city of New York, and State of New York.

HERMAN L. STRONGSON.

